The present invention relates to medical devices and methods. More specifically, the invention relates to vertebral body replacements and methods of spanning a space formed upon removal of an intervertebral disc.
Back pain takes an enormous toll on the health and productivity of people around the world. According to the American Academy of Orthopedic Surgeons, approximately 80 percent of Americans will experience back pain at some time in their life. In the year 2000, approximately 26 million visits were made to physicians' offices due to back problems in the United States. On any one day, it is estimated that 5% of the working population in America is disabled by back pain.
One common cause of back pain is injury, degeneration and/or dysfunction of one or more intervertebral discs. Intervertebral discs are the soft tissue structures located between each of the thirty-three vertebral bones that make up the vertebral (spinal) column. Essentially, the discs allow the vertebrae to move relative to one another. The vertebral column and discs are vital anatomical structures, in that they form a central axis that supports the head and torso, allow for movement of the back, and protect the spinal cord, which passes through the vertebrae in proximity to the discs.
Another form of spinal injury involves injury or deformity of the vertebra themselves. When one or more vertebrae is fracture or deformed by tumor or other causes and results in pain and discomfort, surgery is often required. Traditionally, surgical procedures for vertebral replacement have involved removal of the vertebra and fusion of the two vertebrae above and below the missing vertebra. It is necessary to replace the removed vertebra to maintain spacing of adjacent vertebrae. Oftentimes, pins, rods, screws, cages and/or the like are inserted between the vertebrae to act as support structures to hold the vertebrae and graft material in place while they permanently fuse together. These vertebral body replacement procedures generally focus on rigidly fusing the adjacent vertebrae and preventing motion.
However, it would be desirable to achieve immobilization of the vertebrae adjacent a removed vertebral body and maintain spacing between the adjacent vertebrae without the complete rigidity of traditional interbody fusion.
Another problem associated with the typical vertebral body replacement procedure is the subsidence of the cage into the vertebral body. The typical vertebral body replacement cage is formed with a large percentage of open space to allow the bone to grow through and form the bridging bone which immobilizes the vertebrae. However, the large amount of open space means that the load on each segment of the cage is significantly higher than if the cage surface area was larger. This results in the cage subsiding or sinking into the bone over time and allows the space between the vertebrae to collapse.
Therefore, a need exists for improved vertebral body replacement and method for spanning a space and maintaining spacing between two vertebrae after removal of an intervertebral body. Such improved method and intervertebral body replacement would avoid the need for growth of bridging bone between the remaining vertebrae.